Passenger transport devices such as escalators and moving walkways are generally known and are efficient devices for the transportation of passengers. Escalators are typically used for transporting passengers in vertical direction, such as from one storey of a building to another storey, while moving walkways are normally used for the transportation of passengers in horizontal direction or at a slight incline of up to 12° from one point to another point. The length and width of the passenger transport device are selected in dependence of the expected passenger traffic for the respective application.
Escalator steps and pallets are designed as one-piece or multi-piece components, wherein the pieces, as a rule, are manufactured by way of casting, extruding, forging processes and the like. A number of steps are usually connected by means of two traction mechanisms to form a step band of an escalator. Similarly a number of pallets are joined to form a pallet band in the same way. A moving walkway or an escalator, as a rule, comprises a support structure or framework with two redirection areas, between which the pallet band or step band is revolvingly guided.
The connection between the traction means and the step or the pallet must be secure and long-lasting, since if the connection comes undone while the passenger transport device is in operation, this can have catastrophic consequences for the users.
The WO 03/051754 A2 discloses a pallet band, the pallets of which are fastened by screws and carrier elements to the traction means. The disadvantage of this type of connection consists in that a very large number of screws per pallet have to be used in order to achieve a sufficiently secure connection. The large number of screws, from a manufacturing point of view, is not only cumbersome and expensive, but also has a large impact on assembly time. But since there is a need for replacing steps and pallets or the traction means due to damage or wear or after a predefined time period, this assembly time occurs not only during the manufacture of an escalator or a moving walkway, but also repeatedly during maintenance of these passenger transport systems.
Furthermore the screws are arranged in a vertical direction and therefore have an almost parallel alignment with the pressure load direction of the pallet or step. The amplitudes of vibrations occurring in operation however, have mainly the same alignment, as a result of which the tightened screws may become loose. Settling effects also in the area of the screw connections may lead to a loss in screw pre-tensioning force and thus to a loosening of the screw connection. For this reason additional screw locks are often used. This means however additional expenditure with regard to material, logistics and assembly, and it also carries the risk of omitting to fit the locks, of imperfections in the screw lock itself or of an erroneous assembly result.